ASoC: qcom: dt-bindings: add bindings for lpass tx macro codec

This binding is for LPASS has internal codec TX macro which is
for connecting with Soundwire TX codecs like WCD938x.

Signed-off-by: Srinivas Kandagatla <srinivas.kandagatla@linaro.org>
Reviewed-by: Rob Herring <robh@kernel.org>
Link: https://lore.kernel.org/r/20210211122735.5691-6-srinivas.kandagatla@linaro.org
Signed-off-by: Mark Brown <broonie@kernel.org>